Researches On The Damage Mechanism Of Fracturing Fluid To The Low Permeability Sandstone Gas Reservoir

Low permeability sandstone gas reservoir is one of the most important areas of China's prospective increasing potential production. Improve the development level and exploit effective of low permeability sandstone gas reservoir are the important guarantee for natural gas business sustainable development. Up to now, Sulige gas field in Ordos basin is proven to be china's largest complete land-based gas field. Moreover, it is also a typical "low permeability, low pressure, low abundance" gas reservoir. Now upper palaeozoic low-permeability sandstone gas reservoir in Sulige is the main exploration object, but it is difficult to achieve the value of industrial exploitation without stimulation measures. Fracturing becomes the most important and effective stimulation methods in low-permeability sandstone gas reservoir development. As inflowing fluid of fracturing reformation, fracturing fluid can not only transmit pressure and carry proppants to the hole, but also it's the main source of reservoir damage, it will bring about various degrees damage to the reservoir. Consequently, correct evaluations of the fracturing fluid performance, analysis of potential harm to the reservoir and reveal of the main damage mechanism have a directive function to the fracturing fluid Optimization, performance improvement and low-permeability sandstone gas reservoir effective development.Analyze water existence forms in porous media. Based on that, apply the unsteady-state constant pressure gas drive method combined with nuclear magnetic resonance (NMR) T2 spectrum technology to probe into the establishment of irreducible water saturation and gas-water seepage law under different gas flooding conditions of low permeability sandstone gas reservoirs. Use the displacement multiple to measure the establishment of irreducible water saturation by gas drive method under an average pressure, and determine the optimum displacement multiple under this condition. Analyze of the variation of water saturation at different stages of gas drive and irreducible water saturation under the influence of the displacement pressure. Analyze of the correlation between irreducible water saturation and reservoir physical property. In addition, experimental study on the core irreducible water saturation formed by centrifugal method after the gas drive experiment, and accurately gain the irreducible water saturation of low permeability sandstone gas reservoir in the Sulige gas field by making a synthesis for gas drive method and centrifugal method.Apply the scanning electron microscope (SEM) and X-ray diffraction (XRD) technology tc analysis of the Clay type, content and occurrence features of low permeability sandstone gas reservoir. Use the constant rate mercury injection technology to probe into the micro-pore-throa features of cores. Apply NMR T2 spectrum technology to experimental study on the damage mechanism of fracturing fluid of low permeability sandstone gas reservoir in the Sulige gas field Combining with conventional flowing experimental methods and the parallel rock matching methoc research on physical simulation experiment of the damage mechanism of guar gum fracturing fluid acid fracturing fluid and surfactant (VES) fracturing fluid is carried out. The experiments can give an objective and accurate evaluation of the water sensitivity damage,water blocking and thickener/VES damage caused by three types of fracturing fluid, Then analyze the causes resulting in damage and the main damage mechanism of each fracturing fluid system to reservoirs, establish (?) new method of researches on the damage mechanism of fracturing fluid to the low permeability sandstone gas reservoir. On this basis, Comprehensive evaluation of the performance of eacl fracturing fluid system, proposed a scheme of fracturing fluid optimization of low permeability sandstone gas reservoir in the Sulige gas field.